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Largest ever study of awareness during general anaesthesia published

News, 10 September 2014

Accidental awareness is one of the most feared complications of general anaesthesia for both patients and anaesthetists. Patients spontaneously report this failure of general anaesthesia in approximately one in every 19,000 cases, according to the NAP5 report published today.

Known as accidental awareness during general anaesthesia (AAGA), it occurs when general anaesthesia is intended but the patient remains conscious. This incidence of spontaneous patient reports of awareness is much lower than estimates of awareness when patients are specifically asked about it after anaesthesia, which are as high as 1 in 600.

The findings come from the largest ever study of awareness, the 5th National Audit Project (NAP5), which has been conducted over the last three years by the Royal College of Anaesthetists (RCoA) and the Association of Anaesthetists of Great Britain and Ireland (AAGBI). The researchers studied 3 million general anaesthetics from every public hospital in UK and Ireland, and studied more than 300 new reports of awareness.

Professor Tim Cook, Consultant Anaesthetist in Bath and co-author of the report, commented: “NAP5 has studied outcomes from all anaesthetics in five countries for a full year, making it a uniquely large and broad project. The project dramatically increases our understanding of anaesthetic awareness and highlights the range and complexity of patient experiences. NAP5, as the biggest ever study of this complication, has been able to define the nature of the problem and those factors that contribute to it more clearly than ever before. As well as adding to the understanding of the condition, we have also recommended changes in practice to minimise the incidence of awareness and, when it occurs, to ensure that it is recognised and managed in such a way as to mitigate longer-term effects on patients.”

The extensive study showed that the majority of episodes of awareness are short-lived, occur before surgery starts or after it finishes, and do not always cause concern to patients. Despite this, 51% of episodes led to distress and 41% to longer-term psychological harm. Sensations experienced included tugging, stitching, pain, paralysis and choking. Patients described feelings of dissociation, panic, extreme fear, suffocation and even dying. Longer-term psychological harm often included features of post-traumatic stress disorder.